1/* crypto/dh/dh_check.c */ 2/* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com) 3 * All rights reserved. 4 * 5 * This package is an SSL implementation written 6 * by Eric Young (eay@cryptsoft.com). 7 * The implementation was written so as to conform with Netscapes SSL. 8 * 9 * This library is free for commercial and non-commercial use as long as 10 * the following conditions are aheared to. The following conditions 11 * apply to all code found in this distribution, be it the RC4, RSA, 12 * lhash, DES, etc., code; not just the SSL code. The SSL documentation 13 * included with this distribution is covered by the same copyright terms 14 * except that the holder is Tim Hudson (tjh@cryptsoft.com). 15 * 16 * Copyright remains Eric Young's, and as such any Copyright notices in 17 * the code are not to be removed. 18 * If this package is used in a product, Eric Young should be given attribution 19 * as the author of the parts of the library used. 20 * This can be in the form of a textual message at program startup or 21 * in documentation (online or textual) provided with the package. 22 * 23 * Redistribution and use in source and binary forms, with or without 24 * modification, are permitted provided that the following conditions 25 * are met: 26 * 1. Redistributions of source code must retain the copyright 27 * notice, this list of conditions and the following disclaimer. 28 * 2. Redistributions in binary form must reproduce the above copyright 29 * notice, this list of conditions and the following disclaimer in the 30 * documentation and/or other materials provided with the distribution. 31 * 3. All advertising materials mentioning features or use of this software 32 * must display the following acknowledgement: 33 * "This product includes cryptographic software written by 34 * Eric Young (eay@cryptsoft.com)" 35 * The word 'cryptographic' can be left out if the rouines from the library 36 * being used are not cryptographic related :-). 37 * 4. If you include any Windows specific code (or a derivative thereof) from 38 * the apps directory (application code) you must include an acknowledgement: 39 * "This product includes software written by Tim Hudson (tjh@cryptsoft.com)" 40 * 41 * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND 42 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 43 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 44 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 45 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 46 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 47 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 48 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 49 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 50 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 51 * SUCH DAMAGE. 52 * 53 * The licence and distribution terms for any publically available version or 54 * derivative of this code cannot be changed. i.e. this code cannot simply be 55 * copied and put under another distribution licence 56 * [including the GNU Public Licence.] 57 */ 58 59#include <stdio.h> 60#include "cryptlib.h" 61#include <openssl/bn.h> 62#include <openssl/dh.h> 63 64/*- 65 * Check that p is a safe prime and 66 * if g is 2, 3 or 5, check that it is a suitable generator 67 * where 68 * for 2, p mod 24 == 11 69 * for 3, p mod 12 == 5 70 * for 5, p mod 10 == 3 or 7 71 * should hold. 72 */ 73 74int DH_check(const DH *dh, int *ret) 75{ 76 int ok = 0; 77 BN_CTX *ctx = NULL; 78 BN_ULONG l; 79 BIGNUM *t1 = NULL, *t2 = NULL; 80 81 *ret = 0; 82 ctx = BN_CTX_new(); 83 if (ctx == NULL) 84 goto err; 85 BN_CTX_start(ctx); 86 t1 = BN_CTX_get(ctx); 87 if (t1 == NULL) 88 goto err; 89 t2 = BN_CTX_get(ctx); 90 if (t2 == NULL) 91 goto err; 92 93 if (dh->q) { 94 if (BN_cmp(dh->g, BN_value_one()) <= 0) 95 *ret |= DH_NOT_SUITABLE_GENERATOR; 96 else if (BN_cmp(dh->g, dh->p) >= 0) 97 *ret |= DH_NOT_SUITABLE_GENERATOR; 98 else { 99 /* Check g^q == 1 mod p */ 100 if (!BN_mod_exp(t1, dh->g, dh->q, dh->p, ctx)) 101 goto err; 102 if (!BN_is_one(t1)) 103 *ret |= DH_NOT_SUITABLE_GENERATOR; 104 } 105 if (!BN_is_prime_ex(dh->q, BN_prime_checks, ctx, NULL)) 106 *ret |= DH_CHECK_Q_NOT_PRIME; 107 /* Check p == 1 mod q i.e. q divides p - 1 */ 108 if (!BN_div(t1, t2, dh->p, dh->q, ctx)) 109 goto err; 110 if (!BN_is_one(t2)) 111 *ret |= DH_CHECK_INVALID_Q_VALUE; 112 if (dh->j && BN_cmp(dh->j, t1)) 113 *ret |= DH_CHECK_INVALID_J_VALUE; 114 115 } else if (BN_is_word(dh->g, DH_GENERATOR_2)) { 116 l = BN_mod_word(dh->p, 24); 117 if (l != 11) 118 *ret |= DH_NOT_SUITABLE_GENERATOR; 119 } 120#if 0 121 else if (BN_is_word(dh->g, DH_GENERATOR_3)) { 122 l = BN_mod_word(dh->p, 12); 123 if (l != 5) 124 *ret |= DH_NOT_SUITABLE_GENERATOR; 125 } 126#endif 127 else if (BN_is_word(dh->g, DH_GENERATOR_5)) { 128 l = BN_mod_word(dh->p, 10); 129 if ((l != 3) && (l != 7)) 130 *ret |= DH_NOT_SUITABLE_GENERATOR; 131 } else 132 *ret |= DH_UNABLE_TO_CHECK_GENERATOR; 133 134 if (!BN_is_prime_ex(dh->p, BN_prime_checks, ctx, NULL)) 135 *ret |= DH_CHECK_P_NOT_PRIME; 136 else if (!dh->q) { 137 if (!BN_rshift1(t1, dh->p)) 138 goto err; 139 if (!BN_is_prime_ex(t1, BN_prime_checks, ctx, NULL)) 140 *ret |= DH_CHECK_P_NOT_SAFE_PRIME; 141 } 142 ok = 1; 143 err: 144 if (ctx != NULL) { 145 BN_CTX_end(ctx); 146 BN_CTX_free(ctx); 147 } 148 return (ok); 149} 150 151int DH_check_pub_key(const DH *dh, const BIGNUM *pub_key, int *ret) 152{ 153 int ok = 0; 154 BIGNUM *tmp = NULL; 155 BN_CTX *ctx = NULL; 156 157 *ret = 0; 158 ctx = BN_CTX_new(); 159 if (ctx == NULL) 160 goto err; 161 BN_CTX_start(ctx); 162 tmp = BN_CTX_get(ctx); 163 if (tmp == NULL || !BN_set_word(tmp, 1)) 164 goto err; 165 if (BN_cmp(pub_key, tmp) <= 0) 166 *ret |= DH_CHECK_PUBKEY_TOO_SMALL; 167 if (BN_copy(tmp, dh->p) == NULL || !BN_sub_word(tmp, 1)) 168 goto err; 169 if (BN_cmp(pub_key, tmp) >= 0) 170 *ret |= DH_CHECK_PUBKEY_TOO_LARGE; 171 172 if (dh->q != NULL) { 173 /* Check pub_key^q == 1 mod p */ 174 if (!BN_mod_exp(tmp, pub_key, dh->q, dh->p, ctx)) 175 goto err; 176 if (!BN_is_one(tmp)) 177 *ret |= DH_CHECK_PUBKEY_INVALID; 178 } 179 180 ok = 1; 181 err: 182 if (ctx != NULL) { 183 BN_CTX_end(ctx); 184 BN_CTX_free(ctx); 185 } 186 return (ok); 187} 188